This book constitutes the refereed proceedings of the 26th International Conference on Practical Aspects of Declarative Languages, PADL 2024, held in London, UK, during January 17–19, 2024. The 13 full papers included in this book were carefully reviewed and selected from 25 submissions. The accepted papers span a range of topics related to functional and logic programming, including reactive programming, hardware implementations, implementation of marketplaces, query languages, and applications of declarative programming techniques to artificial intelligence and machine learning.